Coolant feeding device of machine tool

ABSTRACT

The present invention prevents coolant from leaking out of a valve ( 23 ) after a feed pump ( 4 ) stops feeding the coolant, and diminishes a time-lag between the onset of feeding the coolant and mist generation, when the feed pump ( 4 ) starts feeding the coolant again. In the machine tool of this invention, the coolant is fed from a feed pump ( 4 ) into a mist generating device ( 13 ) provided on the tip of a spindle ( 8 ) by way of a feed line ( 7 ), and a valve ( 23 ) is provided at an inflow part for coolant of the mist generating device ( 13 ) to be closed when the coolant pressure within the feed line ( 7 ) lowers below a fixed level. A coolant sucking and delivering ( 2 ) sucks a fixed amount of coolant in the feed line ( 7 ), when the feed pump ( 4 ) stops feeding the coolant. On the other hand, the device ( 2 ) feeds a fixed amount of coolant into the feed line ( 7 ), when the feed pump ( 4 ) begins feeding the coolant.

FIELD OF THE INVENTION

This invention relates to a coolant feeding device of a machine tool.

BACKGROUND OF THE INVENTION

Prior art references (such as the Japanese Patent Publication No. 66437of 1997) have disclosed machine tools that feed coolant from a feed pumpto a mist generating device at the tip of a spindle through a feed line,and that is provided with a valve means at a coolant inflow portion ofthe mist generating device. Here, the valve means is to close a coolantpath when coolant pressure within the feed line lowers below a fixedlevel.

In the above conventional machine tools, compressed air is mingled withthe coolant inside the feed line, fed from the mist generating device.When the feed pump stops feeding the coolant, compressed air pressurelowers, and then the air expands, thereby causing a little coolantleakage out of the valve means (this phenomenon is called liquiddropping).

The liquid dropping is a waste of coolant. Besides, it widens a timi-lagbetween the onset of the feed pump and mist production by the mistgenerating device. Moreover, when generating mist again, the coolantwhich remains in the mist generating device may spout at a stretch,thereby polluting a work piece and a working environment.

An object of this invention is to provide a coolant feeding device ofthe machine tool that can solve the above problems.

SUMMARY OF THE INVENTION

To achieve the above object, the present invention is characterized by amachine tool that feeds coolant from a feed pump to a mist generatingdevice on the tip of a spindle by way of a feed line. In this machinetool, a cylinder chamber for compressed air and a cylinder chamber forcoolant are provided oppositely. Besides, pistons (30) (31) are providedto the cylinder chambers (28) (29), respectively, and integrated intoone body. Moreover, a coolant sucking and delivering means is providedwith a compression spring to press the pistons in a specific directionfor each cylinder chamber. The means sucks a fixed amount of coolant inthe feed line, when the feed pump stops feeding the coolant.Furthermore, the means feeds a fixed amount of coolant into the feedline, when the feed pump begins feeding the coolant.

When the above coolant sucking and delivering means sucks the coolant,the coolant pressure within the feed line lowers at a stretch.Accordingly, usual liquid dropping is prevented.

Beside, when the coolant sucking and delivering means spouts thecoolant, the coolant pressure within the feed line rises at a stretch.Accordingly, the coolant is immediately fed into the mist generatingdevice in connection with the onset of coolant feed from the feed pump,thereby bring about a good response of mist generation.

This invention can be materialized as follows.

At a coolant inflow part of the mist generating device is provided avalve means that is closed when the coolant pressure within the feedline is below a fixed level. The valve means is closed immediately, whenthe feed pump stops feeding the coolant. Therefore, usual liquiddropping is prevented more certainly. On the other hand, when the feedpump begins feeding the coolant, the valve means is open immediately.This enables rapid mist generation.

Besides, the coolant sucking and delivering means sucks the coolantinside the feed line into the cylinder chamber at need, and dischargesthe sucked coolant into the feed line at need. According to this means,sucking and discharging coolant is easy.

Moreover, the piston is driven by a compressed air fed into the mistgenerating device for producing mist. Since the compressed air forproducing the mist is used for driving the piston, driving mechanism forthe piston is simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the main part of a machine tool according tothis invention.

FIG. 2 is an explanatory view diagraming the main part of the machinetool.

FIG. 3 is a sectional view showing surroundings of a mist generatingdevice of the machine tool according to this invention.

FIG. 4 is a front view showing a part of a coolant injection nozzle ofthe mist generating device.

FIG. 5 shows a modification of the above embodiment.

PREFERRED EMBODIMENT OF THE PRESENT INVENTION

A detailed explanation follows about embodiments of the presentinvention with reference to drawings.

In the drawings, 1 is a spindle unit, 2 is a coolant sucking anddelivering means, 3 is a coolant tank, 4 is a feed pump, 5 is a sourcefor compressed air, 6 is a feed line for compressed air, and 7 is a feedline.

The spindle unit 1 comprises a spindle 8, a pulley 10, a clamp actuator12 and a rotating joint 14. The spindle 8 is rotatably held in a holdingcylinder 9 for the spindle. On the rear of the spindle 8 is fixed thepulley 10, into which rotational motive power is input. The clampactuator 12 is provided on the rear end of the spindle 8 to clamp orunclamp a pull-stud 11 a at the rear end of a tool holder 11, which isfixed on the tip end of the spindle 8. The rotating joint 14 is providedon the rear of the actuator 12 to feed the coolant and the compressedair from the outside of the spindle 8 into a mist generating device 13,which is provided inside the tip of the spindle 8.

The mist generating device 13 is integrated into a cylindrical holder16, which engages with a clamp 15 to clamp the pull-stud 11 a. Adetailed explanation will follow.

As shown in FIG. 3, a mist discharge cylinder 17, a compression spring18, a cylindrical valve 19, a mist generating cylinder 20, and a coolantinjection nozzle 21 are arranged inside an inner hole of the cylindermember 16 in this order from the front thereof.

The discharge cylinder 17 is provided with a flange 17 a on its rearend. The flange 17 a is engaged with a stage 16 a of the inner hole ofthe cylindrical holder 16, thereby preventing the discharge cylinder 17from coming out to the forward f1, and contacting the tip face of thedischarge cylinder 17 to the rear face of the pull-stud 11 a.

The cylindrical valve 19 is provided with a stage 19 a on itscircumferential face, and pressed backward by the compression spring 18which is situated between the stage 19 a and the rear face of thedischarge cylinder 17. Here, the cylindrical valve 19 is closed when therear face 19 b contacts to the front face of the mist generatingcylinder 20, and open when the rear face 19 b is away therefrom.

The mist generating cylinder 20 is a cylindrical member, provided with alongitudinal air path groove 20 a on the circumferential face of themist generating cylinder 20, a mist exit hole 20 b having a comparativelarge diameter at the inner front, and a rear inner hole 20 c at theinner rear thereof, into which a front 21 a of the injecting nozzle 21is inserted. The inner hole 20 c communicates with the air path groove20 a through a side hole 20 d, and with the exit hole 20 b through apath 20 e having a comparative small diameter. Therefore, backwarddisplacement of the mist generating cylinder 20 are prevented by theinjecting nozzle 21.

The injecting nozzle 21 is provided with a flange 21 b on the rearcircumferential face of the front 21 a. The rear of the flange 21 b isfluid-tightly inserted into the tip of a straight coolant feed pipe 22.Besides, at the center of the injecting nozzle 21 is provided a steppedpath 21 c whose rear is open. As shown in FIG. 4, the front wall of thepath 21 c is provided with three injection holes 21 d. Here, the feedpipe 22 is integrated with the spindle 8 to control backwarddisplacement of the injecting nozzle 21.

The rear of the path 21 c is an inflow part for the coolant from thefeed pipe 22, and here is provided a valve means 23. Concretely, acompression spring 24 is inserted into the path 21 c, and its front endis engaged with a stage “a” of the path 21 c. Besides, a globe 25 isprovided to the rear end of the compression spring 24, and a cylindricalvalve seat 26, which closely fits into the feed pipe 22 e, is insertedinto the path 21 c on the rear of the globe 25. Here, the globe 25closes a front opening of the cylindrical valve seat 26. Moreover, anotch 27 is formed relative to the position of the globe 25. When thecoolant pressure is over the fixed level within the feed pipe 22, theglobe 25 is forwardly displaced against elasticity of the spring 18,thereby opening the coolant path. Hence, the coolant flows to the sideof the spring 18 from the valve seat 26 through the notch 27.Conversely, when the coolant pressure lowers below the fixed levelwithin the feed pipe 22, the globe 25 is backwardly displaced by theelasticity of the spring 18. Accordingly, the coolant path is closed,and the flowing of the coolant stops.

The means 2 for sucking and discharging coolant has the followingconstructions. A cylinder chamber 28 for the compressed air and acylinder chamber 29 for the coolant are formed oppositely, and pistons30, 31 are provided to the cylinder chambers 28, 29, respectively. Thesepistons 30, 31 are integrated, and a compression spring 32 is providedto press these pistons 30, 31 in a specified direction f2 for thecylinder chambers 28, 29.

The feed pump 4 has the same construction as the means 2. A cylinderchamber 33 for the coolant and a cylinder chamber 34 for the compressedair are formed oppositely, and pistons 35, 36 are provided to thecylinder chambers 33, 34, respectively. These pistons 35, 36 areintegrated, and a compression spring 37 is provided to press thesepistons 35, 36 in a specified direction for the cylinder chamber 33, 34.

The feed line 6 for the compressed air connects to an upper closed space3 a of the coolant tank 3 and an inlet 14 a for the compressed air ofthe joint 14 through a direction diverter 38 as well as a pressureadjusting device 39. Besides, the feed line 6 diverges before the inlet14 a, and its branch connects to the cylinder chamber 29 through adischarge regulator 40. The feed line 6 reaches the air groove 20 a ofthe mist generating device 13 from the inlet 14 a through a compressedair path 41 which surrounds the feed pipe 22. Moreover, the feed line 6also diverges at the upper stream of the diverter 38, and its branchconnects to the cylinder chamber 34 through a direction diverter 42.

In this case, the adjusting device 39 has a pressure control valve 43 toadjust feed pressure of the compressed air, and a check valve 44 topermit the compressed air in the feed line 6 on the spindle 8 side toflow into the diverter 38. Besides, the regulator 40 has a dischargecontrol valve 45 to adjust a feed rate of the compressed air flowinginto the cylinder chamber 28, and a check valve 46 to permit thecompressed air to flow out of the cylinder chamber 28.

The feed line 7 connects the bottom of the tank 3 to a suction hole ofthe cylinder chamber 33. Besides, it connects a discharge hole of thecylinder chamber 33 to a coolant inlet 14 b of the joint 14. Moreover,the feed line 7 diverges before the inlet 14 b, and its branch connectsto the cylinder chamber 29 for coolant. Furthermore, the feed line 7reaches the inflow part of the mist generating device 13 from the inlet14 b through the straight feed pipe 22.

Here, 47 is a silencer to reduce a noise due to the compressed airflowing out of the diverters 38, 42 to the air. The numeral 48 is adipstick for coolant, and 49 is a cutting edge fixed on the front of thetool holder 11.

A working example and actions of the machine tool will be explained asfollows.

The spindle 8 rotates, when rotations are transmitted to the pulley 12by a not-illustrated motor. During its rotations, when the diverter 38is turned to the feed side of the compressed air, the compressed airreaches the groove 20 a through the joint 14 and the compressed air path41 of the spindle 8, and then flows into the inner hole 20 c through theside hole 20 d. Subsequently, the compressed air spouts toward the exithole 20 b through the path 20 e at high speed. During this process, thecompressed air is flowing into the cylinder chamber 28, therebydisplacing the piston 30 toward the piston 31 against elasticity of thespring 32. Accordingly, the cylinder chamber 29 minimizes its capacity.

At the same time as switching over the diverter 38, the other diverter42 is repeatedly reciprocated between a feed side and an outflow side ofthe compressed air at proper intervals. When the diverter 42 is turnedto the feed side, the compressed air is fed into the cylinder chamber34, thereby pressing the piston 36 toward the piston 35 againstelasticity of the spring 37. On the other hand, when the diverter 42 isturned to the outflow side, the compressed air flows out of the cylinderchamber 34, thereby displacing the piston 35 in a pressing direction ofthe spring 37 by its elasticity.

Since the piston 35 is displaced in connection with the piston 36, thecylinder chamber 33 sucks the coolant inside the tank 3 and dischargesthat, repeatedly. The discharged coolant reaches the valve 23 of themist generating device 13 through the joint 14 and the straight feedpipe 22. When the forward displacement power of the globe 25 due to thecoolant pressure is larger than elasticity of the spring 24, the globe25 is pressed forward, thereby opening the valve 23. Accordingly, thecoolant reaches the front of the inner hole 21 c through the valve 23,and then spouts from here through the injection hole 21 d.

The spouted coolant is heavily mixed with the compressed air in front ofthe injection hole 21 d, and then made into mist. The mist reaches therear end of the pull-stud 11 a of the tool holder 11 through the exithole 20 e, and inner holes of the cylindrical valve 19 and the dischargecylinder 17. The mist spouts outside from a tip opening of the cuttingedge 49 through central holes of the tool holder 11 and the cutting edge49, lubricating a cut part of a work piece “w” during machining it.Besides, when the mist pressure lowers below the fixed level within theinner hole of the discharge cylinder 17, the cylindrical valve 19becomes unbalanced in a longitudinal direction, and is displaced forwardagainst elasticity of the spring 18. Therefore, the rear end of thecylindrical valve 19 is separated from the tip of the mist generatingcylinder 20, and then through a gap therebetween the compressed airinside the groove 20 a flows into an inner hole of the dischargecylinder 20.

During producing the above-mentioned mist, when the diverter 38 isturned to the outflow side, feed of the compressed air into the mistgenerating device 13 stops immediately. Besides, operation of the feedpump 4 also stops, thereby preventing coolant feed into the feed line 7.

On the other hand, since the compressed air in the cylinder chamber 28escapes from the diverter 38, the piston 31 in the cylinder chamber 29is displaced by elasticity of the spring 32. Due to this displacement, afixed amount of coolant is sucked from the feed line 7, thereby loweringthe coolant pressure within the feed pipe 22 at a stretch. Therefore,the valve 23 is closed right after feed of the compressed air stops,thereby preventing the coolant inside the feed pipe 22 from flowing outof the valve 23 into the mist generating device 13. Accordingly, noliquid drops like in the conventional machine tools.

Next, when the diverter 38 is turned to the feed side of the compressedair again under a state that feed of the compressed air stops, thecompressed air is fed into the mist generating device 13 through thefeed line 6 as is mentioned in the above. This compressed air is fedinto the cylinder chamber 28 of the means 2, displacing the piston 30toward the piston 31 against elasticity of the spring 32. Due to thisdisplacement, a fixed amount of previously sucked coolant is extrudedfrom the cylinder chamber 29, and then the extruded coolant is fed intothe feed line 7.

Therefore, the coolant pressure in the feed line 7 on the upper streamof the valve 23 rises at a stretch in connection with feed of thecompressed air, and this risen pressure opens the valve 23 immediately.Thereafter, the coolant fed from the feed pump 4 reaches the injectionhole 21 d through the valve 23. Then, the coolant is made into a mist,and spouted from the tip of the cutting edge 49.

In the above operation, the check valve 46 hastens outflow of thecompressed air in the cylinder chamber 28 and the feed line 6 toward theair. Besides, the control valve 45 changes inflow velocity of thecompressed air into the cylinder chamber 28, and adjusts outflowvelocity of the coolant from the cylinder chamber 29 on the onset offeeding the compressed air into the feed line 6. Hence, the controlvalve 45 changes a speed in increasing pressure of the coolant insidethe feed line 7.

In the above embodiment, the feed pump 4 can be of an optionalmechanism. For example, the piston 36 in the cylinder chamber 34 can bedriven by an electric motor or compressed air irrelevant to the feedline 6.

FIG. 5 shows a modified example of the above embodiment. Here, the mistgenerating device 13 is located around the spindle 8. The mistgenerating device 13 mixes the compressed air fed from the feed line 6and the coolant fed from the feed line 7, producing a coolant mist atthe tip. Then, it spouts the mist toward a portion to be cut by thecutting edge 49.

In this case, though the above valve 23 is not provided to a coolantinflow portion of the mist generating device 13, it may be given atneed.

The feed lines 6, 7 around the spindle 8 are connected to a joint 100fixed on the holding cylinder 9, and from the joint 100 they areelongated to connect to the mist generating device 13 through adeformable double tube 101. Here, a central path 101 a of the doubletube 101 is for the coolant, while a looped path 101 b around it is forthe compressed air.

UTILITY VALUE IN THE INDUSTRY

The present invention has the following effects.

According to claim 1, right after the feed pump stops feeding thecoolant, the means for sucking and discharging the coolant lowers thecoolant pressure within the feed line by sucking a fixed amount ofcoolant. Accordingly, usual liquid dropping and related various badinfluences are prevented.

According to claim 2, right after the feed pump stops feeding thecoolant, the coolant sucking and delivering means lowers the coolantpressure within the feed line by sucking a fixed amount of coolant,thereby closing the valve means at once. Accordingly, usual liquiddropping and related various bad influences are prevented.

Besides, as soon as the feed pump begins feeding the coolant again, thecoolant sucking and delivering means raises the coolant pressure byspouting a fixed amount of coolant sucked into the feed line previously.Therefore, the valve means opens at once, and then the coolant is fedinto the mist generating device. Accordingly, a time-lag between theonset of feeding the coolant from the feed pump and production of themist by the mist generating device is diminished.

According to claim 3, the coolant inside the feed line can be sucked anddischarged by simple and firm mechanism.

According to claim 4, the feed means for the compressed air, which isnecessary to produce the mist, can be partially used as a drivingcoolant sucking and delivering means, and therefor its mechanism issimplified. Besides, feed of the compressed air into the mist generatingdevice can be connected to drive of the coolant sucking and deliveringmeans without any complicated control device.

What is claimed is:
 1. A coolant feeding device of a machine tool thatfeeds the coolant from a feed pump (4) to a mist generating device (13)on the tip of a spindle (8) by way of a feed line (7): wherein acylinder chamber (28) for compressed air and a cylinder chamber (29) forcoolant are provided oppositely; wherein pistons (30) (31) are providedto said cylinder chambers (28) (29), respectively, and integrated intoone body; wherein a coolant sucking and delivering means (2) is providedwith a compression spring (32) to press said pistons in a specificdirection for each cylinder chamber; wherein said coolant sucking anddelivering means (2) sucks a fixed amount of coolant in the feed line(7) when the feed pump (4) stops feeding the coolant; and wherein saidcoolant sucking and delivering means (2) feeds a fixed amount of coolantinto the feed line (7) when the feed pump (4) begins feeding thecoolant.
 2. A coolant feeding device of a machine tool as set forth inclaim 1, wherein said coolant sucking and delivering means (2) sucks thecoolant from the feed line (7) into the cylinder chamber (29), andspouts the coolant into the feed line at need.
 3. A coolant feedingdevice of a machine tool as set forth in claim 1, wherein said piston(31) provided to the cylinder chamber (29) is driven by compressed airto be fed into the mist generating device (13) for producing mist.
 4. Acoolant feeding device of a machine tool that feeds the coolant from afeed pump (4) to a mist generating device (13) on the tip of a spindle(8) by way of a feed line (7): wherein a cylinder chamber (28) forcompressed air and a cylinder chamber (29) for coolant are providedoppositely; wherein pistons (30) (31) are provided to said cylinderchambers (28) (29), respectively, and integrated into one body; whereina coolant sucking and delivering means (2) is provided with acompression spring (32) to press said pistons in a specific directionfor each cylinder chamber; wherein said coolant sucking and deliveringmeans sucks a fixed amount of coolant in the feed line (7) when the feedpump (4) stops feeding the coolant; wherein said coolant sucking anddelivering means feeds a fixed amount of coolant into the feed line (7)when the feed pump (4) begins feeding the coolant; wherein valve means(23) is provided to a coolant inlet of the mist generating device (13);and wherein said valve means (23) closes when coolant pressure withinthe feed line (7) decreases to below a fixed level.
 5. A coolant feedingdevice of a machine tool as set forth in claim 4, wherein said coolantsucking and delivering means (2) sucks the coolant from the feed line(7) into the cylinder chamber (29), and spouts the coolant into the feedline at need.
 6. A coolant feeding device of a machine tool as set forthin claim 4, wherein said piston (31) provided to the cylinder chamber(29) is driven by compressed air to be fed into the mist generatingdevice (13) for producing mist.